Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 7f1acd4edf18efc0…

MALICIOUS

RTF / .DOC

1.70 MB First seen: 2022-04-08
MD5: c63e57acad1451467785b67252ed45ca SHA-1: 249d38594a5a5b287727ce2b552fc6ee47e38077 SHA-256: 7f1acd4edf18efc028ebf8f1c2dec15e7b9c982078d5da2340cba9242e6fca4d
240 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File: User Execution T1559.001 Component Object Model Hijacking T1059.001 PowerShell

The RTF file contains multiple indicators of malicious activity, including OLE object data and embedded OLE objects. Critically, it fires heuristics related to CVE-2017-11882, indicating the exploitation of a known vulnerability in the Equation Editor. The presence of a large, hex-encoded OLE object suggests it is hiding a payload. The decoded OLE object has a high entropy, further supporting this. The attack pattern is consistent with exploiting this vulnerability to execute arbitrary code.

Heuristics 6

  • Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact attribution was not recovered.
  • Split hex Equation Editor ProgID + OLE object critical RTF_EQUATION_EDITOR
    RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
  • \objupdate forces OLE activation high RTF_OBJUPDATE
    RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1778KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 2 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001dc5.bin
31486a020bff3456253241fbd45d6afc0969b89a45b31c130751e1ca322b87d3		 rtf-objdata-decoded RTF \objdata at offset 0x1DC5 889406 bytes

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